An electromagnetic contactor for opening/closing a current path is designed such that a movable contact thereof is driven by an exciting coil and movable plunger of an electromagnetic unit. In other words, while the exciting coil is in a non-excited state, a moving core is urged by a return spring and thereby the movable contact comes to an open state where the movable contact is separated from a pair of fixed contacts disposed at a predetermined interval. By exciting the exciting coil when the movable contact is in the open state, the moving core is attracted to a fixed core and moved against the return spring. As a result, the movable contact contacts the pair of fixed contacts entering a closed state (see Patent Document 1, for example).    Patent Document 1: Japanese Patent Publication No. 3107288
Incidentally, the electromagnetic device of the conventional example described in Patent Document 1 is configured to have a tubular fixed core disposed on the upper side of a central opening of a coil frame for holding a coil, and a moving core (referred to as “movable plunger” hereinafter) disposed at a predetermined interval from the fixed core while being urged between the fixed core and a yoke by a return spring. The yoke is configured to have a U-shaped yoke main body and a bush installed in a through-hole formed in a central piece of the yoke main body. A non-magnetic bottomed cylindrical body is interposed between the bush and the movable plunger.
Therefore, by exciting the exciting coil in the open state in which the fixed core and the movable plunger are separated away from each other at the predetermined interval and a bottom surface of the movable plunger is inserted in the through-hole of the central piece of the yoke main body, the fixed core attracts the movable plunger and raises the movable plunger. As a result, the movable contact contacts the fixed contact and enters the closed state. However, there is an unsolved problem that, due to the rising of the movable plunger in this closed state, the magnetic flux density between the movable plunger and the yoke main body drops, reducing the attractive force between the fixed core and the movable plunger.